Lack of built-in flash on OM-D annoying or frustrating?

Very annoying. The whole raison d'etre of m43 is that it's more compact than a DSLR. I don't want a flash on a hotshoe.  And despite some purists' objections, I think having at least the option of a built-in flash is incredibly useful; as fill flash in bright light, or in case of emergency in really dark situations where high ISO's aren't enough or are undesirable.